


Once in a Lifetime

by heavenlyspur



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Eventual Romance, F/M, Fluff, Friendship/Love, Mutual Pining, Other Additional Tags to Be Added, Pre-Time Skip, Rare Pairings, Slow Burn
Language: English
Status: In-Progress
Published: 2020-11-30
Updated: 2020-11-30
Packaged: 2021-03-09 20:55:03
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,675
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27802645
Author URL: https://archiveofourown.org/users/heavenlyspur/pseuds/heavenlyspur
Summary: Against better judgement, Dedue forms a friendship with his beloved Professor. Perhaps he can let his guard down long enough to let her become part of his life.Semi-cohesive chapters on how their relationship develops during time spent together pre- and post-timeskip. Minor character relationships mentioned later on.Slow-burn/pinning, but there will probably be smut later on because I can't help myself.
Relationships: Dedue Molinaro/My Unit | Byleth
Kudos: 9





	1. Dormitory Meet-Cute

**Author's Note:**

> *Any feedback is appreciated.  
> **This is my upload so I'm a little shy. I'm working on pacing, dialogue, and story-telling. You know, pretty much everything!
> 
> I had such a hard time choosing between Dimitri and Dedue when I played FE3H, and thought it was finally time to contribute to the underrated Byleth x Dedue ship :)
> 
> Uploading what I currently have written to get it off my mind so I can focus on school work again!

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The halls of Garreg Mach Monastery were abuzz with rumors about the new professor joining the Officers Academy and who had apparently chosen to lead the Blue Lions house this year. Dedue had not paid much attention to the rumors as his focus was on His Highness, the crown prince of the Faerghus Kingdom and leader of the Blue Lions.

Dedue did hear one rumor he knew was true: that the new professor was apparently a strong mercenary who saved His Highness and the other house leaders from a bandit ambush. It was a rare moment Dedue was not accompanying the young future king, and if possible, it would be one of the last times he had thought.

If this new professor was able to protect His Highness in that instant while Dedue was unable to, then he needn’t worry about who taught the Blue Lions for their stay at the monastery. As long as the professor proved they could give proper instruction, then he could continue his job serving His Highness and all would be well.

While laughter from his peers filled the Blue Lion classroom, Dedue set off to find the dormitories. He sidestepped fiery-haired Sylvain with his similarly heated personality, attempting to charm a student from the Black Eagles house. As the female student leaned in and giggled into Sylvain’s ear it was clear it must have been working.

Leaving them behind, Dedue pushed some of his white short-cropped hair out of his face with a calloused hand and a small sigh. He then grabbed the luggage he had been carrying with him and set off on the cobblestone paths of the campus.

Disregarding Sylvain as being typical Sylvain, Dedue turned his attention to his mental list of tasks to complete for the day.

The first task at hand was to find his own dorm room, “ _then I must set up His Highness’ room and secure the perimeter_ ” he thought, clutching a stack of large tomes and two duffel bags embroidered with the Faerghus sigil.

While His Highness was tied up in a meeting between the faculty at the academy and house leaders, Dedue could at least be of use by prepping His Highness’ dorm room. After all, the students were here to learn warfare techniques, leadership, and other essential skills to prepare them for their futures, so they might as well be comfortable while doing so.

On top of the tomes was a small piece of parchment paper with the dorm placements for all the students sketched on it. Approaching the dormitories, Dedue glanced at the paper again, etching the room placements into his mind. He needed to make sure he knew where everyone was in case anything was to happen to His Highness or any other of the students of the Blue Lions house.

“ _Okay_ , _my room is on the ground level, second room from the end. His Highness should be directly above me, but the staircase is a minor annoyance_ ” he thought analytically while glancing up at the entrance to the second floor of the dormitory.

If only there was a direct route between them. They were separated by a mere floor but if something were to happen up there, Dedue would need to move fast.

“ _Or rather I must always be at the ready outside His Highness’ room so it never comes to that_ ” Dedue quashed the thought of some imaginary scenario happening, although it was part of his job to prepare for any and all circumstances.

His sense of duty to the crown prince would prevent anything from happening. Additionally, Dedue was a mere retainer and not nobility, so he understood that he had to be on the ground level with the rest of the commoners.

It was the way Garreg Mach had always been set up the student placements at the Officers Academy, nobility with nobility on the more private second floor and commoners on the ground level. Dedue made note of the rooms as he passed them, only Mercedes, Annette and Ashe would be on this level and the rest: Ingrid, Felix, Sylvain, and High Highness would be on the second floor. Passing each room Dedue soon found his, the second to last dorm all to himself.

Setting the bags on the ground with his right hand, he briefly fumbled trying to juggle the texts in his left and retrieving a key from his pocket with his newly free hand.

“Do you need any help?” Dedue heard from a soft voice next to him.

Dedue turned and saw a young woman with light skin and muted blue hair watching him, her hair was a lovely color that he had not seen before he thought to himself. In Duscur where Dedue was raised most of his people, including his family, inherited dark olive skin and bright silvery white locks.

Realizing he wasn’t used to interacting with others; the Blue Lion students or the Faerghus royalty (excluding His Highness), much less a pretty stranger, Dedue fumbled to find words for a moment as the keys chattered against the paved walkway outside his new room.

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Byleth was in her dorm for a moment retrieving a piece of paperwork the Archbishop of Garreg Mach and leader of the Church of Seiros, Rhea, had given her. It was a contract Byleth was given to confirm her as a new professor for the Academy with the terms and conditions explained in brief. Byleth was to bring the contract signed to her first official meeting with the other professors and faculty. She was also to meet with her chosen house leader, Dimitri.

This was all a whirlwind to Byleth, who until a couple days ago, was a mercenary wandering the land with her father Jeralt and his rag-tag team. Now she was to be a professor to students her own age from the three nations of Fódlan. Between this and Byleth’s strange dreams involving a girl calling herself Sothis, Byleth had a lot to think about and now was _not_ the time.

Grabbing the contract and about to rush over to Rhea’s chambers, Byleth opened her door to see someone outside the dorm next to hers. Even though she was the new professor rooms within the monastery were sparse, and her father had also taken a position rejoining the Knights of Seiros within the church. Therefore she was given one of the last furnished rooms available, a ground level dorm next to other students from all three houses. It wasn’t a big deal to Byleth, she thought it would be a great chance to get to know more people near her own age.

This student in front of her, trying to hold a stack of large books and unlock the dorm door, gave Byleth a great first chance to introduce herself. Asking if he needed help, he just glanced at her with an indecipherable look.

“ _Okay Byleth, not a great start_ ” she thought glancing at the stack of books, “ _Hmm important-looking texts judging from that sigil, probably shouldn’t put those on the ground_ ” she finished the thought.

“I can hold those if you want, it looks like you’ve got a lot on your hands” Byleth said filling the brief silence.

“That will not be necessary, it is part of my job to see to it that His Highness’ possessions do not fall into other’s hands. I mean no offense” the tall student replied tersely.

Byleth noticed a singular golden earring glisten in the sun as he shook his head lightly. The jewelry design was unlike anything she had seen before, and it softened yet suited his masculine face very well. She smiled at the thought.

Byleth sensed no hostility from the unnamed student and observing his formal address pushed on,

“His Highness? If you mean Dimitri, that must make you a Blue Lion” she stated kindly to ease any tension and establish familiarity.

“My name is Byleth-I’m actually the new professor for the Blue Lions, and I promise you I will not run off with the texts”

She paused briefly before continuing and gesturing to her own door, “in fact as you can see I am also your new neighbor, so even if I did, you would know exactly where to find me” Byleth finished her thought with a wink at the end hoping to coming across as friendly the student in front of her.

It must have worked a little because he briefly introduced himself, “Very well my name is Dedue, His Highness’ retainer”.

Byleth smiled politely at her new acquaintance, his voice was pleasant and deep, and he spoke with very little frill and fluff. Straight to the point and nothing more she noticed.

He then quickly picked up the keys not relinquishing the books in his other hand and opened the door in front of him.

“I appreciate the offer, and I suspect we will see each other in the future. Good day, Professor” the student known as Dedue offered before entering his dorm with nod.

Byleth knew when she wasn’t needed and with a nod back, locked her own door.

“It was nice to meet you Dedue, and I hope to see you later!” she called back as she headed off briskly to Rhea’s chambers.

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With the exit of his new professor, Dedue set aside one of the duffle bags on the bed in the dorm room. Dedue took a moment to look over the modest room; the bed was in the far left corner covered with crisp cream linen sheets, next to the bed was a small bedside table, a dresser was also provided, and against the wall he shared with the professor was a small desk with a built-in shelf. The room was fashioned with several small candle holders, as most of the electricity the monastery had access to was maintained within the main building and adjacent corridors.

Taking a relaxing breath in, the room smelled faintly of lavender.

Dedue rarely smiled, but within these chambers after the brief encounter with the new professor he felt the corners of his mouth upturn slightly. Her blue hair and radiant, almost violet, eyes stuck in his mind’s eye for almost a moment too long.

“How odd,” Dedue mused to himself at the encounter while retrieving his scant possessions from the smaller of the two duffel bags.

As a foreigner to Fódlan and hailing from the infamous lands of Duscur nonetheless, Dedue was lucky to be met with indifference from Fódlans. Instead, it was much more likely he would be met with varying degrees of scorn. Instead, the professor regarded him kindly in that brief moment, and even implicated seeing him again. Of course they would see each other in the classroom and during training battles, but Dedue felt that maybe she meant it differently, in almost a friendly capacity like how Sylvain, Felix, and Ingrid spoke to one another.

Dedue had a sense of obligation to His Highness and didn’t have time for extraneous friendships. 

“It would be wise to maintain a distance from her” he finished his thought, shaking his head as some sort of definitive way to clear his mind before heading upstairs to unpack the crown prince's belongings. 


	2. The Walk Back

**Summary for the Chapter:**

> Dimitri invites Byleth for evening work sessions in the library. The two of them seem to enjoy each other's company while Dedue looks on. One fateful evening, Dimitri asks Dedue to walk Byleth to the dorms and the two of them briefly discuss friendship.
> 
> That's basically it! :)

The first big event the Blue Lions took part of was the annual mock battle between the three houses. In the time leading up to it Byleth spent her time trying to get to know all the students at the academy, and at the mock battle she quickly asserted herself as a sharp-witted tactician and masterful swordsperson on the battlefield. It was easy for anyone to see why the monastery recruited her to teach the future leaders of Fódlan’s nations. The Blue Lions ended up winning handily, letting Black Eagle students preoccupy themselves with the Golden Deer, while the Blue Lions exploited this blind spot to secure high ground against both houses.

Anyone could have easily boasted about besting the other houses at the afterparty, but Byleth didn’t. Instead she made sure she paid every student, regardless of their house, a compliment on some aspect of the skills they demonstrated on the battlefield. Dedue was thoroughly impressed watching her lead on and off the battlegrounds and it seemed other students were as well. Dedue quickly felt that he could place trust in her with His Highness’ life if a battle went awry, but part of him still felt it would be best to keep her at a distance as he had done with the rest of the students at the academy.

It seemed, however, that his Professor was doing whatever she could to thwart his plan.

The week of lessons following the battle had went well, Dedue sat in the front of the classroom next to Dimitri which allowed him to fully absorb each of the professor’s lessons. Byleth seemed a little nervous at the start but by the end of the week she grew in confidence. As their last lesson of the week wrapped up, Dimitri excused himself from Dedue’s company while the rest of the class filed out of the room.

Dedue watched from his seat as Dimitri walked up to the Professor’s desk.

“Professor, I must thank you for choosing to instruct the Blue Lions. Your lesson today was phenomenal. I’ve never truly considered learning about weapons other than the spear, but you’ve convinced me that to excel on the battlefield it is important that I understand at minimum the basics of the others” His Highness spoke excitedly.

“Well thank you, Dimitri! I really appreciate your feedback, I hope the rest of the class feels similarly”, the Professor responded scratching the back of her head.

She did so bashfully Dedue noted, as if she could accept the His Highness’ praise out of kindness but still had reservations about her teachings.

“I can’t speak much for everyone, especially not for someone as say Felix for example, but Dedue perhaps…” His Highness trailed off and both the Professor and His Highness looked directly at Dedue now.

“You could appreciate the Professor’s lecture too, correct?” Dimitri offered. His clear blue eyes watched Dedue expectantly.

With His Highness and the Professor’s eyes on him, Dedue felt like an intrusion. Looking at them for a moment he cleared his throat and agreed.

“Well that settles it!” Dimitri clasped his hands together, the metallic gauntlets he wore with his uniform clinking together noisily in the otherwise quiet room.

“You at least have Dedue and I on your side, and Dedue’s approval is always hard won so count yourself lucky!” Dimitri said with a chuckle and turned his attention back to the Professor.

Dedue felt his cheeks flush at His Highness’ comment about him, so he excused himself to wait outside the classroom for the two to finish their conversation.

The Professor watched as Dedue rose from his seat to exit the room. Her eyes unconsciously scanned his body as he left, his boots making rhythmic taps as he walked out. Realizing how this may look, she quickly shook her head and returned her attention to Dimitri.

Noticing this brief shake, but misinterpreting it as wariness against his loyal retainer, Dimitri felt the need to speak up for Dedue,

“Dedue means no harm. He is most trustworthy and my closest companion”.

The Professor responded quickly, “Oh no no no!” raising her hands in front of her.

“I know Dedue doesn’t,” Byleth spoke low hoping Dedue wouldn’t hear her talking about him and misinterpret it as gossip on her part.

“I enjoy talking to him, the very little we’ve spoken. He’s also quite strong and impressive on the battlefield, taking on both Caspar and Ferdinand during or mock battle!”.

Dimitri perked up at the Professor’s comments, “I’m certainly glad you think so, Professor” he said.

“That also reminds me what I wanted to say or rather ask you before we adjourn for the day. As of late I have spent many evenings mostly alone in the library studying. If you’d like to join me there sometime to discuss lesson plans, battle plans, or any whatever plans, your company would certainly be enjoyed” Dimitri said very well-rehearsed.

He must have spent some time thinking about asking her or was just flexing his natural charismatic talents, Dedue thought as he leaned in slightly from outside the door frame. He had heard everything including the Professor’s comment about his own abilities on the battlefield. Dedue smiled lightly at her noticing him during the mock battle and then his mouth quickly formed an intense straight line after His Highness extended the library invite to the Professor.

It wasn’t that Dedue was mad that His Highness would invite the Professor to the late-night library sessions, rather, as a retainer Dedue always watched over Dimitri during these times. This meant if the Professor took up His Highness’ offer, they would likely spend extended periods of time together.

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For the next couple of weeks, Byleth did take up the offer to work in the library with Dimitri and Dedue occasionally. Most evenings she and Dimitri would work at one of the large, wooded desks in the library typically in an empty corner for privacy. Dedue would occasionally participate in conversation when they called on him, but he spent most of his time reading at another desk or taking brief walks through the halls.

For a few hours in the evenings she and Dimitri would alter between working independently and chatting about whatever randomly came up. Dimitri would typically pour over various large record books with beautiful gold-leafed accents. Byleth never tried to pry into what Dimitri was looking for within these books, instead, she would focus on outlining broad lesson plans for the entire class and the more individualized lessons for each student.

Sometimes Dedue would notice himself watching them closely, rather watching Byleth as she laughed over a random joke with Dimitri. Dedue was pleased that His Highness was forming new companionships and had looked genuinely happy, but he wondered did it have to include their Professor?

His thought was interrupted as Byleth gathered up her materials earlier into the evening than normal. Typically, the group would adjourn for the night as the last of the candles had withered down into nothing. The still-lit candles of the library illuminated her face in an amber hue as she thanked Dimitri and Dedue for their time.

“Leaving early this time Professor?” Dimitri asked not looking up from the parchment he was scribbling notes onto.

“Yes, we have another large mission from the Archbishop to complete this weekend. I’d like to get some extra rest to prepare for it. It may be a good idea for you as well, Your Highness” Byleth replied, the last of her materials secured away in her work tote bag that rested on her work bench.

“The same goes to you, Dedue” Byleth said coyly, turning now to Dedue who had begun getting up from his own desk.

Dimitri looked up at this moment, pen still in his hand, “You know you may call me by my given name, Professor. While I appreciate the sentiment, I shall sleep once my work is done” and returned his attention to the paper once again.

“Dedue, please see to it that our Professor makes it back to her dorm safely. It’s much too dark out tonight and the path to the dorms is not one to make alone at this hour” Dimitri stated to his retainer.

Byleth turned to Dedue in this moment “Very well, shall we?” she stated, swinging her leg over the wooded bench she had been seated at.

Byleth’s typical outfit consisted of a lightly armored corset top with black cut-out tights patterned intricately with a pair of black shorts. The flesh of her toned stomach peeked out slightly from above her shorts. The shorts were easy to move in, but occasionally rode up in those moments she lifted her legs up. She instinctively grabbed the cuffs in between her thighs and pulled them down as she had done a thousand times before.

This time however, as she looked up from doing so, she made direct eye contact with Dedue. At this moment Dedue cleared his throat and looked away from her, his aqua-colored eyes darting towards the ground. Byleth in unison also looked away, her cheeks becoming uncomfortably warm.

He was embarrassed from getting caught staring at his Professor, and lightly tugged at his short ponytail before addressing Dimitri.

“Very well, Your Highness. I shall see to it Professor makes it to her room and then I will return for you right away”.

Dimitri glanced up at the comment, completely oblivious to the awkward interaction that had just occurred between his two companions.

“Absolutely not, Dedue” he spoke with authority.

“I’ve got a lot more work to do tonight, and like Professor said we could both do with some extra rest. Your room is right next to Professor’s after all, so it makes more sense for you to turn in for the night as well rather than coming to retrieve me” Dimitri concluded.

Dedue knew to pick his battles with His Highness, and he wasn’t exactly displeased to walk the Professor back to their respective rooms. With a slight bow, he strode out of the library no extra comments necessary.

Byleth also nodded to Dimitri before reminding him not to stay up too late. She grabbed her leather tote bag and hoisted it onto her shoulder before joining Dedue.

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“May I carry your bag, Professor?” Dedue offered quietly to Byleth as they walked through the empty hallway to the cathedral exit.

Byleth took up the offer relinquishing her bag over to him when their hands briefly touched. Dedue flinched slightly, his battle reflexes betraying him in that instant.

Noticing this, Byleth frowned slightly unsure what his reaction to such a slight touch was supposed to mean. She straightened her back, unsure why her ego seemed so bruised, and proceeded to walk curtly out of the cathedral into the crisp night air.

Dedue sensed the Professor’s mood shift, he didn’t mean to put a damper at the end of their night. His brow furrowed, “ _it must have been the touch_ ” he thought.

Not one to leave things linger, Dedue felt the need to remedy the situation immediately and stopped under one of the few cathedral lights illuminating the exit. Byleth halted as well and looked up at him with raised eyebrow expectantly.

“Professor. I am aware that you show kindness to all your students, but I am also aware of my status in Fódlan as a man from Duscur. Regardless of your good intentions it would be wise for you to maintain a distance from me to avoid any rumors that may befall you.”

“Ahh…” Byleth said quietly, looking down at her feet understanding what Dedue was trying to communicate to her.

As a mercenary, she frequently traveled and worked with people from all over Fódlan and occasionally lands beyond. Her father may not have taught her all the prim and proper things some of the students raised in nobility learned, but he did instill in her a strong sense of self and moral values. She didn’t judge others based on where they came from or from the many stereotypes that seem to run rampant in certain Fódlan social circles.

She shifted her weight from the heels of her boots to the tip of her toes, rocking slightly.

“I guess I can read between the lines, you don’t want my reputation or whatever to be tainted by being associated with you?” she asked with her eyes still focused on the ground boring a mental hole into the stone.

Dedue watched his Professor as she seemed to close up in response to his advice. He bit on his bottom lip and watched as a couple locks of her blue hair fell in front her face. With a light breeze, her hair swayed like the nighttime tides ebb and flow onto the shore.

A small part of him he wondered if a Dedue in a different universe would have pushed that hair behind her ear as he’d seen her do many times before. It was too bad that alternate Dedue wasn’t in present Dedue’s place, for he couldn’t be that informal with his Professor. She was his Professor, for Goddess’ sake!

“That is…essentially what I mean, yes. I am glad you understand” he stated as kindly as he could muster in the moment, “now shall we head back to the dorms?” he asked, moving on from the topic.

Byleth chuckled at her student in front of her. The outside light shone from above highlighted his strong bone structure. He could have looked intimidating; he was over a head taller than her and towered over her with this ominous light. Except, for whatever reason he wasn’t intimidating to her. They had done several small missions for Rhea, fought small groups of bandits, beaten a band of thieves and mages, she had also seen him cook in the cafeteria several times, and had witnessed his devotion to Dimitri wherever they went. She had learned he was impressive and stoic both on and off the battlefield.

She chuckled to herself lightly and they resumed their stroll.

“It’s a little silly for you to say that, especially as you’re carrying my bag for me right now. You talk about distancing yet the simple acts of kindness you repay me could also be misinterpreted” she retorted, looking over at him locking eyes in friendly combat.

Dedue offered nothing in response letting her playfulness wash over him. His Highness had jested with him before which Dedue had always ignored, as a royal retainer he didn’t “jest”. With her it felt more natural and it briefly reminded him of his time as a youth…before the Tragedy. 

As they continued in silence, Byleth crossed an arm over her chest, her other arm was lifted and clasped her neck as she thought.

“Yes, tonight we can just continue our walk to the dorms, but I see no reason why we can’t continue being friends as normal” she spoke aloud, confirming it to herself rather than offering it up to him to respond.

“I can certainly deal with any rumors _if_ it comes to that. I do prefer to live my life without the pressures of what others think” she paused before adding,

“It’s a luxury that I realize you may not have in your position, but I hope you know Dimitri and I have your back. I suspect others in your class might come to feel that way if you let them in” she offered up finally, hoping her sincerity was able to come across.

What she had said caught him off guard, hitting him straight in the chest. He nodded as they walked up the final walkway to their dorm rooms.

“You may be right, Professor. I will take your words into consideration” he said softly now in front of their doorways as she unlocked her door. 

“I think His Highness appreciates your company a lot, and as a class we all have a lot to learn from you…” he trailed off.

Byleth turned to him and smiled, only the moon and stars for light at their disposal. Her eyes had adjusted to the darkness, and she saw his figure away from her now as he stepped away to open his own door. She reached out with a gentle touch and rested a hand on his forearm.

“Thank you Dedue, for walking me back tonight and for the conversation, I hope you too in time will appreciate my company”

“Goodnight” she said with a small squeeze of his arm before letting go and entering her respective room. 

In his own room, Dedue could feel through the long sleeves of his uniform where her hand had touched his arm. A smile crept up his face like vines on brick, their tendrils reaching up towards the sun yearning for its warmth. He slept soundly that night.

**Notes for the Chapter:**

> This is pretty much all I have written at this point. I took my Thanksgiving Break and channeled some of that down time into the first two chapters posted here.
> 
> I haven't written for fun in a very very long time, so this has been an interesting exercise. I don't know if this chapter is any better than the first, but I enjoyed writing it.
> 
> Thanks for reading.

**Author's Note:**

> The next chapter I have written out is more classroom/studying related bringing in Dimitri some more as well! (yay love triangles)  
> The 3rd chapter I plan on writing in the greenhouse scene before the timeskip and from there we'll see!
> 
> Thanks for reading!


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